Angew. Chem. Int. Ed. 2009, 48, 4406 –4408 Using Azobenzene-Embedded Self-Assembled Monolayers To　Photochemically Control Cell Adhesion Reversibly nano biomedicine

Cell attachment activity of fibronectin can be duplicated by small synthetic fragments of the molecule Michael D. Pierschbacher & Erkki Ruoslahti Horst Kessler and co-workers Nature 309, 30-33 ,1984 J. AM. CHEM. SOC. 2005, 127, 16107-16110 They used cyclo RGDfK [cyclo (Arg-Gly-Asp-d-Phe-Lys)] in PMMA disc. Phototriggering of Cell Adhesion by Caged Cyclic RGD Peptides** MC3T3 E1 mouse osteoblasts were seeded on the BSA blocked substrate. Attached cells were quantified by an ELISA. Aranzazu del Campo* Angew. Chem. 2008, 120, 3236 –3239

Introduction.. Many applications in biology. Triggering with different external stimuli. Problem: Existing technologies have mostly relied on irreversible control. Solution: Azobenzene having isomerization property at different wavelength. They used the idea that RGD in a background of PEG terminated SAMs allows specific interaction between cells and surface and will prevent non specific adhesion.

Experimental.. They construct a mixed SAMs in two ways. NHS (N- hydroxysuccinimide)

Rinsing with PBS : 3 times (pH 7.4) Preparation of SAMs.. They used electron beam evaporation of gold (20nm) onto clean glass cover slips with a thin layer of chronium (8nm) to promote adhesion. Selected way is Total conc: SAMs-- 2 mmol L-1 0.01% 0.1% 1% Time of dipping into ethanolic solution 4 hour Rinsing with PBS : 3 times (pH 7.4) : 5 times (pH 8.6) : 3 times (pH 7.4) : Milli-Q water 3 times : Pure ethanol 3 times : Dried with N2 GRGDS conc:-- 2 mgmL-1 Ratio of 3 and 2 Time of dipping in PBS solution of GRGDS --20 minute

Cell Adhesion.. Cell used : Murine NIH 3T3 fibroblasts. Trans rich state : 5 hour visible light and stored in dark for 3 days. Cis rich area : 10 hour UV irradiation.

Conclusion.. SAMs allow us to design and quickly obtain a surface that allows reversible control of cell adhesion on a molecularly well-defined surface. Believe that by combining with the ability to spatially address surface chemistries, the technique presented herein can be used to control the mobility of parts of a single cell a single cell, or groups of cells directionally at will. thank you